Development and effect of drug release from simvastatin loaded sodium alginate micro beads

The objective of the present study was to prepare the microbeads of Simvastatin loaded with sodium alginate to provide control release of drug delivery system. So, the design of drug delivery system was to improve and enhance the bioavailability of drug. The Simvastatin loaded microbeads were prepared by the ionic gelation method using polymer such as sodium alginate as a natural substance. Simvastatin loaded sodium alginate microbeads were formulated by different cross linking agent like CaCl₂, BaCl₂, ZnCl₂ and FeCl₃ in different ratio. The microbeads were spherical, free flowing exhibited drug content uniformity and high drug encapsulation efficiency. The swelling and drug release behavior depends upon amount of cross linking agent used in the microbeads. This released the drug up to 24 hours where beads released the drug up to 6 hours. The FTIR analysis of drug, polymers and the optimized formulation indicated the compatibility of the drug with the polymers. The DSC studies confirmed the drug polymer interaction in the microspheres. The SEM studies influence the rate of drug release from the microbeads. The present study concludes that the swelling and In-vitro release behavior of Simvastatin loaded sodium alginate microbeads can be considered as a promising control release drug delivery system.


Introduction
The pure forms of drug or therapeutic active substances are not administered as such but they are fabricated as dosage form of specified size, shape and texture.So, all the possible delivery routes like oral, topical and parenteral to maximize therapeutic response must be considered (1).The oral route has been the preferred route of administration for many drugs.The administration of conventional dosage form in a particular dose and time through oral route is possible to control the constant dose concentration in blood plasma (2).This results fluctuation in plasma drug level and leads to several dose related toxic effects and reduces patient compliance (3).After oral ingestion the materials are stored in the stomach and mixed with the GI fluid, converted into liquid mass and then pass gradually into the upper small intestine.Thus, the GIT represents a primary barrier for oral absorption of drugs (4).
The term controlled release is the delivery systems to deliver the drug locally or systemically for a known time period (5).The release of active ingredients from controlled release drug delivery produces the release rate not only in advanced manner but also repeatedly from one unit to another (6).Most of the oral control release products are enter into the GI-tract and the fluid slowly penetrate through the outer layer of polymer matrix which includes the dissolution, swelling and formation of thick hydrodynamic layer (7,8,9).
Simvastatin is an antihyperlipidemic drug.The oral route is the most commonly used and preferred route of choice for the delivery of drugs.It is rapidly absorbed by the liver after oral administration and undergo metabolism (10).The primary action is to increase the excretion of low density lipoprotein receptors in the liver which occurs in response to inhibition of HMG-COA reductase.It leads to increased clearance of low density of lipoproteins (11).Cholesterol from the plasma with a subsequent reduction in both low densities.Lipoproteins and cholesterol (12).Thus, Simvastatin arrests a key step of cholesterol biosynthesis in the liver and is widely used in the treatment of hypercholesterolesterolemia and dyslipidemia (13).After, oral administration, Simvastatin is metabolized to its Bhydroxy acid form (Simvastatin acid) by the cytochrome-3A system.So it is used to reduce LDL-cholestrol (14).The ionotropic gelation technique was selected to prepare Simvastatin loaded microbeads such as sodium alginate along with formulated by different cross linking agent due to its simplicity and low cost (15,16).The aim of the present study was to prepare and evaluate the microbeads as a new control release system for Simvastastin.

Material and methods
Simvastatin was obtained as gift sample from Aurobindo Pharma Hyderabad.Sodium Alginate was obtained from Nice Chemicals, Kerala and Natural Industries, Mumbai.All the chemicals were analytical grade for the purpose of research.

Preparation of microbeads
400 mg of sodium alginate, 40mg Simvastatin, 1.25gm cross linking agent &10ml of water taken for preparation of microbeads.4% w/v of sodium alginate was prepared by adding 400mg of sodium alginate to 10 ml of distilled water in a 25ml of beaker and subjected to heat.To the above slurry, 40mg of Simvastatin was added with constant stirring by magnetic stirrer for specific period of time to get deflocculated suspension.Then, 5% CaCl₂ was prepared by adding 1.25gm of CaCl₂ to 25ml distilled water in a 100ml of beaker.The bubble free polymers was taken in a 10ml syringe (20mm size) and added drop wise into cross-linking media of 25ml cacl2 solution to get spherical capsules.The drug loaded microbeads was allowed to stand for 2hrs curring time (18).After the specific period of time, microbeads were taken out by filtration and allowed to dry for 24 hrs.Similarly, polymers were crosslinked with BaCl₂, ZnCl₂ and FeCl₃.The formulation variables were followed the above procedure and subjected to dry for 24 hrs.

Evaluation of micro beads
The average particle size of the prepared beads was measured by sieve analysis methods.The average particle sizes of different formulation are shown in the Table 1.The yield of formulated microbeads was evaluated by comparing the practical yield with that of the theoretical yield.Swelling property of microbeads was studied by a measuring the percentage of water uptake as a function of time.Evaluation of swelling behavior of Simvastatin loaded sodium alginate was carried out in phosphate buffer of pH 7.4.20mg of beads were placed in watch glass containing 5ml of 0.1N HCl in respective media.The schedule experiment was carried out at room temperature.The swelling beads were removed at a definite time interval i.e. 30min, 1hr, 1.30min, 2, 3 and 4hrs.Then dry at room temperature for 24 hrs and then dissolved in phosphate buffer.The fractional change in weight was measured by using digital balance during swelling study.The percentage of water uptake was calculated by using following formula (19).All the studies were conducted in triplicate (n=3)

Determination of drug loading and drug encapsulation
Accurately weighed 100mg of Simvastatin loaded with sodium alginate was taken, crushed and suspended in 250ml of phosphate buffer of pH 7.4.The resulting solution was transferred into a stoppered conical flash and the flask was shaken occasionally for 24hrs.Next day it was stirred for 20min.using magnetic stirrer (20).The solution was filtered through whattman filter paper.The drug content in the filtrate was analyzed by using UV-Visible spectrophotometer (Shimadzu 1800USA) at 238.6nm against appropriate blank.The obtained absorbance was plotted on the standard curve to get the exact concentration of the entrapped drug.The drug loading and drug encapsulation efficiency of beads were calculated by using following formula.The flow properties of microbeads were evaluated using carr's Index.The results were averaged from three determinations.The angle of repose of the microbeads was determined by the fixed funnel and the free standing cone method.The Hausner ratio was estimated by using following formula.

In-vitro dissolution studies
Drug release study was carried out in dissolution test apparatus, USP type-I(TDT-06L),Electro lab.Mumbai.In-vitro dissolution study is an important tool in the evaluation of formulation and drug release profile from microbeads was examined in the buffer solution to mimic the various physiological region of GI-tract.The composition of dissolution medium was consisting of 0.238gm of phosphate buffer; 0.019 gm of potassium dihydrogen phosphate, 0.8gm of NaCl containing 0.5 gm (SLS).The volume of dissolution medium was 500ml of pH 7.4 phosphate buffer using USP type-I dissolution apparatus and the bath temperature was maintained at 37 °C ± 0.5 °C.The micro beads were placed in the dissolution vessel and the vessel was covered, the apparatus was operated for 8hrs at 50rpm.At definite time interval, 5ml of the dissolution fluid was withdraw and equal volume of fresh dissolution medium was replaced to maintain the volume of the dissolution medium constant.The withdrawn samples were analyzed spectrophotometrically at 238.6nm UV-Spectrophotometer (Shimadzu 1800USA).Formulation of Simvastatin loaded sodium alginate Simvastatin loaded sodium alginate was subjected to In-vitro dissolution studies.All the studies were conducted in triplicate (n=3)

FTIR Study
The drug polymer interactions were studied by using FT-IR Spectrophotometer (Bruker FTIR Alpha-T Series).The FT-IR Spectra of the pure drug, Simvastatin loaded sodium alginate polymer beads and its interpretations were observed in the microbeads.

Differential scanning calorimetric (DCS) study
The thermal analysis of Simvastatin loaded sodium alginate beads was performed by using DSC (DSC-4000 PerkinElmer).The samples were heated from 30°c to 310°c at an increase rate of temperature 40°c/min.so, heat flow as a function of temperature was measured for the drug and drug polymer mixture.

Scanning electron microscopy (SEM) study
The shape and surface characteristics were determined by SEM method (JSM-IT 700HR) using gold sputter technique.Photographs were scanned with range of 15kv magnification.

Particle size determination
All the microbeads were prepared by ionic gelation method.The prepared microbeads are dried.The average particle sizes of microbeads of different formulations were measured by sieve analysis method.All the microbeads having its own particle size ranged from 391.36µm to 1063.75µm& represented in table no.1

Drug Loading and Drug Encapsulation
All the prepared microbeads were found to be spherical with white in colour.The drug loaded microbeads of Simvaststin with sodium alginate are represented in table no.4.All the prepared microbeads formulations show uniformity of drug content.The drug encapsulation efficiency was in range the of 49.26 to 83.58.Simvastatin loaded sodium alginate microbeads with Bacl₂ as the cross linking agent has shown maximum percentage of drug loading & drug encapsulation efficiency.Hence the batches of microbeads fabricated by using Bacl₂ as cross linking agent was selected as the most efficient one among all the cross linking agent and specifically the DSC & SEM study carried out for this particular cross linking agent.The prepared batches of microbeads were evaluated for micromeritic study such as bulk density, tapped density, carr's index, Hausners ratio & angle of repose i.e. in table no5.The bulk density of different formulation ranged from 0.424 to 0.720 g/ml.The tapped density of different formulation ranged from 0.513 to 0.821 g/ml.The carr's ratio of the different batches of microbeads ranged from 10.20 to 17.78% .The angle of repose of all formulation ranged from 14 to 19.Based on the above micromeritic properties of all the batches, it was concluded that the prepared microbeads had excellent flow properties.

In-vitro dissolution study
Drug release from the microbeads was evaluated in phosphate buffer (рH7.4) at different time intervals.The % release of drug has considered from standard curve was plotted in figure1, 2, 3, 4. The order of drug release from the different formulation with interval of time can be arranged in suitable manner that means initially it shows lesser extent of drug release i.e. 21% to 51% (15min.to 30min.) but gradually it shows better extent of drug release i.e. from 70.84% to 98.06% (up to 6hours).The release of drug was accelerated by the weight loss of the mucoadhesive polymers.The release of the drug was modulated by the diffusion of the drug through the swollen polymeric matrix.

Scanning electron microscopy study
The SEM studies revealed that the simvastatin loaded sodium alginate microbeads was spherical in shape and completely covered with the coat polymer.It can influence the rate of drug release from the microbeads& show in the figure 12,13.

Figure 1
Figure 1 Drug release profile of different micro beads loaded with (a) Ca-alg (b) Ba-alg (c) Zn-alg (d) Fe-alg3.6.FTIR studyThe drug-polymer interaction was carried out by FT-IR spectroscopic study.The FT-IR spectrum of the pure drug shows the characteristic peak at 1070.73cm¯¹& 1695.35cm¯¹due to alcoholic and C=O stretching of the ester group.The FT-IR spectrum of drug loaded Ca-alg bead exhibited peak at 1015.14cm¯¹&1598.97cm¯¹.Similarly, the FT-IR spectrum of drug loaded Ba-alg bead exhibited peak at 676.50cm¯¹& 1582.37cm¯¹.The FT-IR spectrum of drug loaded Zn-alg and Fe-alg exhibited peak at 1022.08cm¯¹ &1590.35cm¯¹along with 1026.64cm¯¹&1708.72cm¯¹.All the peaks are observed by the FT-IR analysis method confirmed that drug polymer interactions was observed in the microbeads &shown in the figure5,6,7,8,9.

Figure 5 SEM
Figure 5 SEM Pattern of (a) Simvastatin (b) Ba-alg beads

Table 1 a
Sieve analysis & particle size determination With CaCl₂

Table 1 b
Sieve analysis & particle size determination With Bacl₂

. Yield of Microbeads The
yield of microbeads was evaluated by comparing the practical yield with that of the theoretical yield.The percentage of yield was ranged from 48.18 to 81.81.The percentage of yield was calculated & presented in table no.2

Table 2
Yield of Micro beads

Table 3 d
Swelling Study With Fecl₃ (4:0) * Swelling Study for Phosphate Buffer is checked for limited time interval

Table 4 a
Drug loading & drug encapsulation With Cacl₂

Table 4 b
Drug loading & drug encapsulation With Bacl₂

Table 4 c
Drug loading & drug encapsulation With Zncl₂

Table 4 d
Drug loading & drug encapsulation With Fecl₃

Table 5
Flow properties of different formulations